Fine particles of salt, water, oil, and other chemical contaminants can be detrimental to canister filters. This contamination, in addition to standard dust and/or other particle loading, reduces life expectancy of canister filters. With higher efficiency filter canisters, loading can further reduce life expectancy and consequently increase operating costs. HEPA level filtration materials in canisters are among the most efficient materials available for canister filters and therefore typically display the shortest life expectancy due to loading and/or contamination.
Gas turbine filtration applications often utilize a filtration membrane layer, such as expanded polytetrafluoroethylene (ePTFE) or high molecular weight polyethylene (HMWPE), for high efficiency filter applications. An increase in the use of membrane filtration has come, at least in part, as a result of an increase in requests for filtration products capable of EPA and/or HEPA grade filtration efficiency. However, HEPA grade filtration may be difficult to achieve in some applications, such as those using marine gas turbines. This difficulty is at least partially due to the operating conditions that these filters are subjected to such as the amount and types of contaminants, as well as a requirement of minimal downtime. Further, industrial environments tend to reduce service life of gas turbine filters. This is generally due, at least in part, to face loading of membrane filtration materials caused by particulate, hydrocarbons, and moisture capture.
These issues have at times been combated in one of two ways. The first is to add a layer of prefiltration directly to the substrate. The second has been to utilize a filter wrap that can help pre-load and extend the life of the HEPA canister filter. These products typically focus only on particulate filtration. However, there are additional contaminants, which can reduce the service life of a filter, that existing prefilters do not address.
Thus, there is a need in the art for overcoming the issues of existing systems.